The present invention relates to a reflection-type overhead projector and, more particularly, to a reflection-type overhead projector which can project transparencies.
Images which can be projected onto a screen with an overhead projector are carried by transparencies with letters and pictures. With, for example, a reflection-type overhead projector, a transparency to be projected is placed on a glass stage comprising a Fresnel mirror and illuminated from above. The image is reflected by the Fresnel mirror and projected by a mirror-and-lens system onto a remote screen.
For preparing materials or originals to be projected with such a reflection-type overhead projector, which should be in the form of transparencies, there is known an overhead projector with a copying device adapted to make a transparency by reflection from a non-transparent but reflecting original. In such an overhead projector, a reflecting original such as a hard copy (which is hereinafter referred to as a reflecting original) is placed on the glass stage in order to scan the reflecting original with an image sensor comprising a CCD line sensor. According to image signals from the image sensor, an image-forming head draws the image on a transparent material so as to provide a transparency. In such an overhead projector, there are used as recording materials heat-sensitive transparent sheets which contain particles or grains which blacken when heated. For blackening these particles, a thermal printing had is used. The combination of the heat-sensitive sheet and the thermal printing head provides an image-recording mechanism which is simple and thus makes the overhead projector practical.
A problem with such an overhead projector is in that the reflecting original has to be illuminated in order to read the image thereon by means of an image-reading head. The reflecting original can be illuminated by a lamp incorporated in the image-reading head. However, the incorporation of the lamp in the reading head results in a large size of image reading head. Furthermore, because the image reading head is unavoidably moved over the reflecting original in order to read the image, it is necessary not only to provide a moving mechanism for the large size of image reading head but also to use an extensible wire for connecting the image-reading head and a power source disposed remote from the image-reading head. Alternatively, it may be convenient to fix the image receiving head to the illuminating lamp as in the case of facsimile machines, electronic writing boards or the like. In this case, the reflecting original should be moved while being maintained flat, which results in a complicated mechanism for moving the reflecting original.